U.S. patent number 7,087,851 [Application Number 11/179,839] was granted by the patent office on 2006-08-08 for microswitch.
This patent grant is currently assigned to Schaltbau GmbH. Invention is credited to Wolfgang Mayer.
United States Patent |
7,087,851 |
Mayer |
August 8, 2006 |
Microswitch
Abstract
The invention relates to a microswitch comprising a housing, a
switching plunger arranged in displaced relationship with the
center of said housing and projecting from said housing, contacts
which are arranged on the housing side located opposite the
switching plunger, and a contact bridge which is adapted to be
transferred from a first to a second switching position through the
switching plunger and a bistable spring, said switching plunger
being provided with a cantilevered arm which projects on one side
and on the projecting end of which a downholder is provided for
positive opening of the contact bridge. In order to improve a
microswitch of the type mentioned at the beginning in such a way
that its overall size can be reduced still further and that a
reliable positive opening operation will take place, the present
invention is so conceived that, on the switching plunger side
located opposite the cantilevered arm, a support projection is
arranged, which acts on a resilient part of the spring in spaced
relationship with the switching plunger, in such a way that, when
the switching plunger is pressed down, a moment (M) will be applied
via the support projection to the cantilevered arm of the switching
plunger in the opening direction of the contact bridge.
Inventors: |
Mayer; Wolfgang (Haar,
DE) |
Assignee: |
Schaltbau GmbH (Munich,
DE)
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Family
ID: |
34936940 |
Appl.
No.: |
11/179,839 |
Filed: |
July 11, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060016678 A1 |
Jan 26, 2006 |
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Foreign Application Priority Data
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Jul 21, 2004 [DE] |
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10 2004 035 193 |
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Current U.S.
Class: |
200/461;
200/405 |
Current CPC
Class: |
H01H
3/001 (20130101); H01H 13/36 (20130101) |
Current International
Class: |
H01H
5/18 (20060101) |
Field of
Search: |
;200/405-409,440,442,449,453,459-461,520 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0618601 |
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Oct 1994 |
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EP |
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0618603 |
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Oct 1994 |
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EP |
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2716746 |
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Sep 1995 |
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FR |
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Primary Examiner: Friedhofer; Michael
Assistant Examiner: Klaus; Lisa
Attorney, Agent or Firm: Townsend and Townsend and Crew
Claims
The invention claimed is:
1. A microswitch (1) comprising a housing (2), a switching plunger
(4) arranged in displaced relationship with the centre of said
housing (2) and projecting from said housing, contacts (22, 23, 24)
arranged on the housing side located opposite the switching
plunger, and a contact bridge (13) which is adapted to be
transferred from a first to a second switching position through the
switching plunger (4) and a bistable spring (14), said switching
plunger (4) being provided with a cantilevered arm (9) which
projects on one side and on the projecting end of which a
downholder (10) is provided for positive opening of the contact
bridge (13), characterized in that on the switching plunger side
located opposite the cantilevered arm (9), a support projection is
arranged, which acts on a resilient part of the spring (14) in
spaced relationship with the switching plunger (4), in such a way
that, when the switching plunger (4) is pressed down, a moment (M)
will be applied via the support projection (12) to the cantilevered
arm (9) of the switching plunger (4) in the opening direction of
the contact bridge (13).
2. A microswitch according to claim 1, characterized in that the
spring (14) acted upon by the support projection (12) of the
switching plunger (4) has a higher spring constant than the contact
bridge (13) acted upon by the downholder (10) of the cantilevered
arm (9).
3. A microswitch according to claim 1, characterized in that the
switching plunger (4) has axially effective guide means (5, 6), the
cantilevered arm (9) and the support projection (12) being located
between these two guide means, and said two guide means being
arranged such that they are displaced relative to one another
transversely to the axial direction of the plunger (4).
4. A microswitch according to one of the claims 1, characterized in
that the lateral distance between the lower guide means (6) and the
axis of the plunger (4) is the same as that between the support
projection (12) and the axis of the plunger (4).
5. A microswitch according to one of the claims 1, characterized in
that the lower guide means (6) is provided with two guide ribs
(6a), which are arranged laterally on the plunger (4) and which
engage complementary guide grooves (7a) of the housing (2).
6. A microswitch according to one of the claims 1, characterized in
that the cantilevered arm (9) and the support projection (12) as
well as the guide ribs (6a) are integrally connected to the
switching plunger.
Description
The invention relates to a microswitch comprising a housing, a
switching plunger arranged in displaced relationship with the
centre of said housing and projecting from said housing, contacts
which are arranged on the housing side located opposite the
switching plunger, and a contact bridge which is adapted to be
transferred from a first to a second switching position through the
switching plunger and a bistable spring, said switching plunger
being provided with a cantilevered arm which projects on one side
and on the projecting end of which a downholder is provided for
positive opening of the contact bridge.
Such a microswitch is known e.g. from EP-618603 B1 which is owned
by the applicant of the present patent application. In the known
microswitch, a bistable spring assembly is provided, which has the
effect that the switch contacts are opened rapidly so as to reduce
the loss of contact material caused due to flashover during the
switching operation. Since it can nevertheless not be fully
excluded that fusing of the switch contacts may occur due to
excessively high currents or due to oxidation, the known
microswitch is so conceived that the cantilevered arm has provided
thereon a downholder which, during the continued movement of the
switching plunger, acts on the contact bridge and leads to positive
opening of the contacts. In microswitches having an extremely small
structural design, the problem arises that the cantilevered arm may
yield due to its dimensioning. In order to achieve a reliable
positive opening operation, it would therefore be necessary to
increase the distance covered by the plunger, or the cantilevered
arm would have to be provided with stronger dimensions. Both
measures would have a negative influence on the overall size of the
microswitch. The possibility of producing the switching plunger
with a cantilevered arm which consists of a material having a
higher modulus of elasticity results in an increase in costs.
It is therefore the object of the present invention to improve a
microswitch of the type mentioned at the beginning in such a way
that the overall size can be reduced still further and that a
reliable positive opening operation will take place.
According to the present invention, this object is achieved in
that, on the switching plunger side located opposite the
cantilevered arm, a support projection is arranged, which acts on a
resilient part of the spring in spaced relationship with the
switching plunger, in such a way that, when the switching plunger
is pressed down, a moment will be applied via the support
projection to the cantilevered arm of the switching plunger in the
opening direction of the contact bridge.
By means of the solution according to the present invention it is
achieved that the downholder of the cantilevered arm is moved
downwards not only in accordance with the distance covered by the
plunger, but that, due to the support on the side located opposite
the cantilevered arm, a rotary motion will additionally act on the
cantilevered arm so that a flex-ion of the cantilevered arm will be
compensated by the torque acting on said cantilevered arm. Hence,
this solution allows a maintenance of the original distance covered
by the plunger and does not necessitate stronger dimensions of the
said cantilevered arm, let alone the use of expensive
materials.
According to an advantageous embodiment, the area of the spring
acted upon by the support projection has a higher spring constant
than the contact bridge at the point where the downholder of the
cantilevered arm presses onto said contact bridge.
According to a further development of the present invention, the
switching plunger has two axially effective guide means, the
cantilevered arm and the support projection being located between
these two guide means, and said two guide means being arranged such
that they are displaced relative to one another transversely to the
axial direction of the plunger. In this way, the opening moment
acting on the lever arm of the cantilevered arm is extended, and
this leads to a further improvement in the positive opening
operation.
According to a preferred embodiment, the lateral distance between
the lower guide means and the axis of the plunger is the same as
that between the support projection and the axis of the
plunger.
According to another preferred embodiment, the lower guide means
comprises two laterally arranged guide ribs which are guided in
complementary grooves provided in the housing wall.
According to a specially preferred embodiment, the cantilevered
arm, the support projection as well as the lateral guide ribs are
integrally connected to the switching plunger.
In the following, one embodiment of the present invention will be
explained in detail making reference to a drawing, in which:
FIG. 1 shows a side view of the microswitch in its starting
position,
FIG. 2 shows a sectional view of the microswitch at the switching
point,
FIG. 3 shows a sectional view of the microswitch at the beginning
of the positive opening operation,
FIG. 4 shows a sectional view of the microswitch, the switching
plunger occupying its final position.
The drawing shows a microswitch in a sectional view, said
microswitch comprising a housing 2 with a housing interior 3. The
housing 2 has arranged therein a switching plunger 4 provided with
two axial guide means 5 and 6 received in two bearing locations 7
and 8 in the housing 2. The guide means 6 disposed in the housing
interior is provided with two guide ribs 6a, which are arranged
laterally on the switching plunger and which, at the associated
bearing location 7, engage two guide grooves 7a provided in the
inner wall of the housing. The guide means 5, which is located
opposite the guide means 6, and the bearing location 8 associated
therewith have an oval cross-section. Furthermore, the free end of
the switching plunger 4 has attached thereto a downholder 10 via a
cantilevered arm. On the switching plunger side located opposite
the cantilevered arm 9 an extension is arranged, which is provided
with a support projection 12. The extension 11 of the switching
plunger 4 acts via the support projection 12 on an end of an
elastically deformable and electrically conductive contact bridge
13 that is provided with a bistable spring assembly comprising a
pressure spring member 14 and a switch contact 15, said contact
bridge end being bent into the shape of a clasp. The pressure
spring member 14 and the contact bridge 13 are implemented as a
one-piece component and rest on both sides on bulges 17 and 18 of
an S-shaped fixed contact 19, the contact bridge 13 being held in
position and being connected to the fixed contact 19 in an
electrically conductive manner. In the engagement area of the
switch contact 15, two fixed contacts 20 and 21 are arranged,
which, like the fixed contact 19, are connected in an electrically
conductive manner to connecting contacts 22, 23 and 24 arranged on
the outer surface of the housing 2. In addition, reinforcements 25
are provided on the straight portions of the clasp-shaped contact
bridge 13.
In the following, the mode of operation of the microswitch will be
explained in detail. At the starting position (FIG. 1), the
pressure spring 14 causes the switch contact 15 to be held in the
first switching position, supported by the force of the resilient
contact bridge 13. In this condition, the connecting contact 22 is
connected to the connecting contact 24 via the fixed contact 19,
via the contact bridge 13, via the switch contact 15, and via the
fixed contact 20. When the switching plunger 4 is pressed into the
housing due to the application of an external force, the extension
11 will act via the support projection 12 onto the bent end of the
resilient contact bridge 13, which will, consequently, undergo
elastic deformation. In the course of this process, the switching
plunger 4 is guided by its two axial guide means 5 and 6 in the
associated bearings 7 and 7a, respectively, as well as 8. Due to
the shape of the guide means 5 and 6 and of the bearings 7 and 8
associated therewith, the switching plunger 4 is supported such
that it is secured against rotation about its axis, but can be
displaced in the axial direction. When the switching plunger 4
continues its movement into the housing (FIG. 2), the line of
action of the pressure spring 14 inclines until the line of action
of the pressure spring 14 comes to lie, in the switching position,
in the surface defined by the contact line between the contact
bridge 13 and the support projection 12 and the connection line
between the transition of the pressure spring 14 and the contact
bridge 13. If the contact between the switch contact 15 and the
fixed contact 20 is not fused, but can be separated freely, the
contact will immediately be switched over with high speed as soon
as the switching plunger 4 is moved into the housing 2 beyond the
switching point. If the contact between the fixed contact 20 and
the switch contact 15 should, however, be fused and prevent
switching over, the downholder 10 will come into engagement with
the contact bridge 13 a short time after the switching plunger 4
has been moved beyond the switching point. Due to the fact that the
plunger 4 rests, on the side located opposite the cantilevered arm
9, via the support projection arranged on the extension 11 on the
bent end of the spring 14, a moment will act on the switching
plunger in the direction of the arrow M, i.e. in the opening
direction of the contact bridge. This moment M has the effect that
the downholder 10 is pressed down further than would, in principle,
be intended by the displacement path of the plunger. The total
amount of play between the switching plunger and the guide means
causes the downholder to be lowered still further. In this way, a
yield of the cantilevered arm caused by bending can be compensated
for more effectively, without any necessity of increasing the
distance covered by the plunger.
In order to guarantee that the fused parts will be separated, the
switching plunger can be pressed into the housing until the
downholder presses the contact bridge 13 directly onto the fixed
contact (cf. FIG. 4).
* * * * *